When a heavy rain falls on conventional existing asphalt or concrete pavement, the rain does not sink into the ground, but flows through roadside drainage system to river, stream, waste water treatment plant or public water area. However, in case of a localized torrential downpour for a short period of time or a heavy rain for a long period of time during the rainy season, the drained rain and water may overflow the river and stream, causing very dangerous and unstable situation. Also, as the rain and water cannot permeate into the conventional existing road or pavement, it obstructs safe passage and causes a lot of inconvenience to pedestrians.
Therefore, in order to overcome such disadvantages of the conventional asphalt or concrete pavement, a permeable concrete pavement comprising aggregates of the size generally less than 13 mm to maintain suitable porosity and strength, and allowing water to seep into the ground through a surface layer and a base layer of the pavement has been suggested and used.
Specifically, the permeable concrete allows rain or water to seep into the ground through pores among the aggregates, fostering the growth of trees and plants, and also prevents flooding of the river by allowing heavy or torrential rain to flow under the earth. Further, as the rain or water does not stay on the permeable concrete pavement, it provides less slippery and much safer walking, jogging or driving conditions.
For these reasons, the permeable concrete pavement has come into use more widely, especially on trails at parks, bicycle paths, tracks for in-line skating, golf-course trails, etc.
Conventional permeable pavements are divided into permeable asphalt concrete and permeable cement concrete. However, the asphalt concrete has disadvantages in that the surface deforms considerably due to high temperatures during the summer season and the pores get clogged up due to the viscosity of the asphalt. Also, the cement concrete is so rigid that people get hurt when they fall on it.
In addition, the conventional permeable-concrete pavement is covered with epoxy pigments for cosmetic view of the surface, but a ramp covered with such epoxy pigments is more slippery than a normal concrete pavement, which causes problems in safety.
Further, because the surface of the concrete pavement is rugged, the surface can peel or break off, and when the pores are covered with dust, the pavement's permeability deteriorates, requiring additional maintenance costs for declogging the pores, i.e. removal of the dust.
As an example to improve the disadvantages of the conventional permeable concrete, Korean Patent No. 404679 (patented on Oct. 27, 2003 entitled “pavement using waste tire chips”) discloses an elastic permeable pavement which comprises a land layer, a filter layer, a rubble layer, a permeable concrete layer, a waste-polyurethane chip layer, and a surface layer from the bottom to the top. Specifically, the filter layer is constructed by spreading small aggregates (sand), and the rubble layer is constructed by pouring and hardening concrete rubbles of the particle size 25 mm or less onto the filter layer. The permeable concrete layer is made by blending aggregates of the particle size 5–13 mm, cement and admixture products with water, and pouring this mixture on the rubble layer and curing it. As a result, the permeable concrete layer has the compressive strength of 100 kg/cm2 or more and the permeability coefficient of 1×10−3 cm/sec or more. Further, the waste-tire chip layer is formed by pouring and spreading in the thickness of 10–20 mm a mixture including waste-tire chips of particle size 2.5–7 mm; a binder comprising 10–25 g of urethane resin, epoxy resin or acrylic resin based on 100 g of the waste tire chips; and 1–4 g of an inorganic pigment on the same base. Furthermore, the surface layer is colored by spraying with the urethane resin, epoxy resin or acrylic resin on the waste-tire chip layer.
The elastic permeable pavement as disclosed in the above patent allows rain or water to penetrate into the ground, and the pavement is resistant to slipping and reduces diffused light-reflection resulted from the water staying on the pavement, thus securing safe passage of pedestrians and providing comfortable vision. Also, as using waste tires which have been one of the environmental pollutants, the pavement not only absorbs impact on foot, but also contributes to the protection of environment and recycling of resources.
However, since the waste tire's smell of rubber lasted for a long time, the pavement using the waste tire could not provide a pleasant sense of smell. Further, since the urethane, epoxy and acrylic resin binders used in the above patent were those available in the market, there have been demands for a special binder which enhances the adhesive strength among pavement materials and maintains the strength and durability of the pavement for a long time.
Further, since the elastic permeable pavement in the above patent used a method of piling up the land layer, the filter layer, the rubble layer, the permeable concrete layer, the waste-polyurethane chip layer and the surface layer from the bottom, in a case where it was not necessary to dig open an existing pavement to newly pave it again, or in a case where there was no sufficient budget for such a pavement, such a pavement construction method of piling up the layers would not be economical in terms of process, time and cost.
Instead, although the existing pavement is not permeable, if it is covered with a permeable pavement so that the rain can pass through the permeable pavement and drain, it would not only be possible to prevent the overflow of the river or stream, but also be very economical since the existing pavement can be used as it is.
Therefore, the inventor of the present invention studied and researched into materials and binders for the elastic permeable pavement, and as a result, the inventor completed the present invention by using waste-polyurethane chips in place of waste-tire chips as a main component of the elastic pavement and developing a binder to secure the binding between an upper polyurethane-chip layer and a lower existing-pavement layer as well as the binding among the waste-polyurethane chips.